A conventional thin client system is classified into a screen transfer type thin client system and a net boot type thin client system (Non-Patent Literature 1).
The screen transfer type thin client system is a system which transfers a screen of an OS (Operating System) operating on a server to a client and inputs from a keyboard and a mouse in the client to the server. In the screen transfer type thin client system, because the OS is executed on the server, the server needs to be provided a high-speed CPU (Central Processing Unit) and a memory of a large capacity.
On the other hand, the net boot-type thin client system is a system in which a client downloads and executes an application (application software) and user data from a server and uploads a changed file to the server. The net boot type thin client system is provided only with a storage, and the client reads and writes directly from and to the storage.
Moreover, the net boot type thin client system is classified into a previously downloading type and an on-demand type.
The previously downloading type system is a system which downloads all files before the OS starts, as in Non-Patent Literature 2. In the previously downloading type system, because all the files are downloaded before the OS starts, including a file which is not usually used, it takes a long time until the OS is started.
The on-demand type system is a system which downloads a file when the file is actually used as in Non-Patent Literature 3. In the on-demand type system, because the file is downloaded when being required, it takes a long time until the OS and the application become ready.
Also, in both types of systems, the decrease (bottle neck) of a response speed for file acquisition occurs intensively on a specific step, and a user feels that a PC (personal computer) becomes very late in some moment.
It should be noted that as related techniques, a thin client system, an apparatus and a program are disclosed in JP 2008-198016A (Patent Literature 1). In this related technique, the net boot type thin client system in which a rich client as a general-purpose PC is available as a thin client has been described.
Also, a file control apparatus is disclosed in JP H09-319624A (Patent Literature 2). In this related technique, a plurality of files and a final use date and time and a storage location of each of these files are stored in a first storage. The file with a low use-frequency is determined based on the final use date and time for every file. The determined file is stored in the second storage.
Also, a system and a method for an on-demand file downloading are disclosed in JP H10-133976 (Patent Literature 3). In this related technique, in order to share a content of a file or a program or data as a content of a memory in a plurality of calculation periods, the program or the data is transferred through a route and downloaded in a computer which uses the program or the data. In this on-demand file downloading method, a necessary part of a file in which the program or the data is stored is specified from a first computer and requested to a second computer which has the originals of the program or the data. The second computer extracts the necessary part of the file requested from the first computer, and copies and transfers it to the first computer in units of packets. The first computer stores the transferred contents in a predetermined area and resumes the processing of the program.